Sorry to revive a very, very old thread. For anyone encountering this challenge today, there’s another much easier solution that may work for most situations. I mentioned it in this related thread: https://forum.bricksbuilder.io/t/select-multiple-recipients-using-form/9927/2?u=beardmancer
If you’re interested in the relevant documentation, it can be found here: https://academy.bricksbuilder.io/article/form-element/#dynamic-fields